Polymer X-ray diffraction

Breiby, D.W. and E.J. Samuelsen. 2003. Quantification of preferential orientation in conjugated polymers using X-ray diffraction. / Polym Sci Polym Phys 41 2375. 

Andjelic, S., jamiolkowski, D., McDivitt, J., Fischer, J., Zhou, J., and Han, C.C. (2001) Time-resolved isothermal crystallization of absorbable PGA-co-PLA copolymer by synchrotron small-angle X-ray scattering and wide-angle X-ray diffraction. Polymer, 42, 8965-8973. 

As shown by the X-ray diffraction, polymer-monomer mixture consists of SmC bilayers. A bilayer is the principal unit cell having either non-polar C2h or polar C2v (b) S5mimetry. The former is incompatible with both ferroelectricity or antiferroelectricity, because such a structure has an inversion centre. On the contrary, in sketch (b) each bilayer is polar with Pq vector located in the tilt plane along the y-axis. In a stack of such layers the direction of Pq alternates and the stmcture (b) is antiferroelectiic in its ground state. Only strong electric field Ey causes the transition to the ferroelectric structure shown in sketch (c) as observed in experiment. Note that both the Pq and P = X Pq vectors are always lying in the tilt plane. 

Assouhne E, Wachtel E, Grignll S, Lustiger A, Wagner H D and Marom G (2001) Lamellar twisting in alpha isotactic poljTrropylene transcrystaUinity investigated by synchrotron microbeam X-ray diffraction, Polymer 42 6231-6237. 

Chen Qun, Kurosu Hiromichi, Ma Lin, and Matsuo Masaru. Elongation-induced phase separation of poly(vinyl alcohol)/poly(acrylic-acid) blends as studied by C CP/MAS NMR and wide-angle X-ray diffraction. Polymer. 43 no. 4 (2002) 1203-1206. 

Baker AME, Windle AH. Evidence for a partially ordered component in polyetbylene from wide-angle X-ray diffraction. Polymer 2001 42 667-680. 

Murthy NS, Bednarczyk C, Minor H. Depth-profiles of structure in single-and multilayered commercial polymer films using grazing-incidence X-ray diffraction. Polymer 2000 41 277-284. 

Kelarakis, A., Yoon, K., Sics, I., Somani, R.H., Hsiao, B.S., Chu, B. Uniaxial deformation of an elastomer nanocomposite containing modified carbon nanofibers by in situ synchrotron X-ray diffraction . Polymer 46(14) (2005), 5103-5117 Karst, D., Yang, Y.Q. Potential advantages and risks of nanotechnology for textiles , AATCCRev. 6(3) (2006), 44-48... 

Noncrystalline domains in fibers are not stmctureless, but the stmctural organization of the polymer chains or chain segments is difficult to evaluate, just as it is difficult to evaluate the stmcture of Hquids. No direct methods are available, but various combinations of physicochemical methods such as x-ray diffraction, birefringence, density, mechanical response, and thermal behavior, have been used to deduce physical quantities that can be used to describe the stmcture of the noncrystalline domains. Among these quantities are the amorphous orientation function and the amorphous density, which can be related to some of the important physical properties of fibers. 

Poly(vinyl fluoride) [24981-14-4] (PVF) is a semicrystaltiae polymer with a planar, zig-zag configuration (50). The degree of crystallinity can vary significantly from 20—60% (51) and is thought to be primarily a function of defect stmctures. Wide-line nmr and x-ray diffraction studies show the unit cell to contain two monomer units and have the dimensions of a = 0.857 nm, b = 0.495 nm, and c = 0.252 nm (52). Similarity to the phase I crystal form of poly (vinytidene fluoride) suggests an orthorhombic crystal (53). 

Gelatin stmctures have been studied with the aid of an electron microscope (23). The stmcture of the gel is a combination of fine and coarse interchain networks the ratio depends on the temperature during the polymer-polymer and polymer-solvent interaction lea ding to bond formation. The rigidity of the gel is approximately proportional to the square of the gelatin concentration. Crystallites, indicated by x-ray diffraction pattern, are beUeved to be at the junctions of the polypeptide chains (24). 

Crystallinity of polypropylene is usually determined by x-ray diffraction (21). Isotactic polymer consists of heHcal molecules, with three monomer units pet chain unit, resulting in a spacing between units of identical conformation of 0.65 nm (Fig. 2a). These molecules interact with others, or different... 

Properties of PET Molding Resins. The fliU crystal stmcture of poly(ethylene terephthalate) has been estabhshed by x-ray diffraction (134—137). It forms triclinic crystals with one polymer chain per unit cell. The original cell parameters were estabhshed in 1954 (134) and numerous groups have re-examined it over the years. Cell parameters are a = 0.444 nm, b = 0.591 nm, and c = 1.067 nm a = 100°, (3 = 117°, and 7 = 112° and density = 1.52 g/cm. One difficulty is determining when crystallinity is fliUy developed. PET has been aimealed at up to 290°C for 2 years (137). 

Chain Structure. The chemical composition of poly (vinyhdene chloride) has been confirmed by various techniques, including elemental analysis, x-ray diffraction analysis, degradation studies, and in, Raman, and nmr spectroscopy. The polymer chain is made up of vinyhdene chloride units added head-to-tail ... 

Cellulose is the main component of the wood cell wall, typically 40—50% by weight of the dry wood. Pure cellulose is a polymer of glucose residues joined by 1,4-P-glucosidic bonds. The degree of polymerization (DP) is variable and may range from 700 to 10,000 DP or more. Wood cellulose is more resistant to dilute acid hydrolysis than hemiceUulose. X-ray diffraction indicates a partial crystalline stmcture for wood cellulose. The crystalline regions are more difficult to hydrolyze than the amorphous regions because removal of the easily hydrolyzed material has Htde effect on the diffraction pattern. 

X-ray diffraction consists of the measurement of the coherent scattering of x-rays (phenomenon 4 above). X-ray diffraction is used to determine the identity of crystalline phases in a multiphase powder sample and the atomic and molecular stmctures of single crystals. It can also be used to determine stmctural details of polymers, fibers, thin films, and amorphous soflds and to study stress, texture, and particle size. 

X-ray Diffraction (XRD) is a powerful technique used to uniquely identify the crystalline phases present in materials and to measure the structural properties (strain state, grain size, epitaxy, phase composition, preferred orientation, and defect structure) of these phases. XRD is also used to determine the thickness of thin films and multilayers, and atomic arrangements in amorphous materials (including polymers) and at inter ces. 

X-ray studies indicate that the vinyl chloride polymer as normally prepared in commercial processes is substantially amorphous although some small amount of crystallinity (about 5% as measured by X-ray diffraction methods) is present. It has been reported by Fuller d in 1940 and Natta and Carradini in 1956 that examination of the crystalline zones indicates a repeat distance of 5.1 A which is consistent with a syndiotactic (i.e. alternating) structure. Later studies using NMR techniques indicate that conventional PVC is about 55% syndiotactic and the rest largely atactic in structure. 

The methods used to characterise polymers are partly familiar ones like X-ray diffraction, Raman spectroscopy and electron microscopy, partly less familiar but widespread ones like neutron scattering and nuclear magnetic resonance, and partly... 

Benzene m air (porous polymer diffusion samplers, thermal desoiption and gas chromatography) Quartz in respirable airborne dusts (X-ray diffraction)... 

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